The plasma profile of fatty acids has been observed in 27 vegetarian adults, their age ranging from 20 to 63 years (13 men, 14 women) with the average period of vegetarian dietary pattern being 8.8 years. A third of the men and a half of the women were lacto-vegetarians, the rest of them were lacto-ovo-vegetarians. The contents of saturated and monounsaturated fatty acids insignificantly decreased in vegetarians when compared with non-vegetarians (n = 26, 12 men, 14 women, average group of non-smokers with mixed nutrition). The results of parameters regarded as positive factors in vegetarian diet and effective in prevention of atherosclerosis are as follows: significantly higher values of linoliec acid C 18:2, a significantly higher ratio of linoliec/leic acids C 18:2/C18:1 and insignificantly higher value of linolenic acid C 18:3, together with an unchanged, or moderately decreased contents of poly-unsaturated fatty acids C 20:4 (arachidonic acid) and C 22:6 (n3; docosahexaenoic acid). Further prooxidative-antioxidative parameters were selected in regard to the theoretical anticipation of risk brought about by increased lipoperoxidation in vegetarians (poly-unsaturated fatty acids-substrate of the process) which is significant in the etiology of cardio-vascular and oncologic diseases. Their favourable values (significantly lower plasma contents of conjugated dienes of fatty acids, significantly higher plasma value of vitamin C, Beta-carotene, vitamin E/cholesterol-protection of LDL, vitamin E/triacylglycerols-protection of fatty acids, 3.5 times more significant positive linear correlation of vitamin E/triacylglycerol versus plasma contents of C 18:2) eliminate the risk of increased lipoperoxidation in vegetarians. (Tab. 3, Fig. 1, Ref. 29.)